1. Field of the Invention
The present invention concerns a greenhouse having a suspended foil or film roof that may be opened when desired. Characteristically, a greenhouse is an artificially heated glass house that is used to start and grow plants such as flowers, decorative plants and vegetables independent of climatic conditions. Such greenhouses are typically equipped with ventilation means and with artificial lighting and sprinkler equipment.
2. Description of Related Art
It has been found to be more cost-effective to cover a greenhouse with a plastic film rather than glass. The flexibility of the plastic film allows the roof to be folded to an open position to expose the plants to natural solar radiation when weather conditions are suitable. The structures that are know in the prior art for opening and closing roofs are laborious in use, expensive to procure and time-consuming in use.
A typical prior art greenhouse with a hanging roof that can be opened, made from inflatable tubular film which is suspended from parallel tightened wires is described in the German Patent 22 23 158. In this construction, when the inflatable tubes are filled with air, they contact each other at the parallel tangential lines and due to their lower position, form a penetration area for rain water. Furthermore, filling them with air limits the penetration of light and ultraviolet rays on the plants in the greenhouse and the air filling will cause the formation of condensation.
Another suspended plastic film roof construction is shown in the German Patent 32 04 026. This roof construction is a hanging form and can be folded in a zigzag manner from a tight wire construction. With this construction, the plastic film covering or roof has multiple layers with air cushions between them and another plastic foil suspended below is permeable to air for humidity that can be controlled in the xe2x80x9cclosedxe2x80x9d position. When moving these multi-layered plastic films and during strong rain or snow, the cover is mechanically unstable.
A relatively simple suspension of a single-layer plastic foil between two posts used as a covering for a greenhouse that features a weighted hanging ridge is shown in French Disclosure No. 2 488 102. No opening mechanism is disclosed. The position of the plastic foil in the direction of radiation can only be changed at the intermediate points.
French Publication No. 2 137 124 describes a greenhouse having a hanging folded roof that can be opened, however it consists of several frames pin-jointed at the bottom, which is the closed state, are deposited onto sloping tight wires. Each individual pin-joint consists of two spaced joints with a gutter interposed between them. The support wires run above across several rows of posts. The sides of the frames facing the joints, which stand vertically when opened, are reciprocally attached with side-to-side linkages that can be moved back and forth. The linkages are directed through necessarily upright positioned cable rolls to guide the folding movement of the frames between an upright standing and positioned at about 45 degrees on the tight wire for control. The construction effort with this greenhouse is very high due to the complexity of the support portion which is complex and is neither located underneath or above the roof, but rather within the movement level of the roof. Shadowing of the plants is also high, both in the open as well as the closed position.
In contrast to the known prior art, the present invention comprises aplastic film greenhouse having a rof that can be easily opened, close or adjusted to several intermediate positions as required. According to the invention, the plastic foil roof stays in any selected position beneath a light but stable support structure from which it is suspended. Even in the completely closed position, the foil or film hangs downwardly. A taught triangular cross-section is formed directed downwardly and the roof is attached to the support structure with two suspension lines. The downward pointing xe2x80x9cridgexe2x80x9d, that is the lowest hanging center line between two suspension lines, is provided with a slope or gradient along the longitudinal axis of the greenhouse in order to let rain water or condensation drain longitudinally. The ridge is weighted to keep the plastic film taut. Preferably, the is accomplished with the use of an elongated hollow pipe that is supported on the longitudinal center axis and is connected to the plastic fil or foil with a snap-in fastener or button. Alternatively, a heavy rod or the like may be used as well. It is important to have balanced weight along this center axis which, on one hand, makes for sufficient tightness of the foil and, on the other hand, does not compromise the light weight construction of the roof assembly.
The suspension lines are moveable perpendicularly to the greenhouse axis along the support structure towards each other and away from each other into any final side position without the use of pin-joints or other supports. In this way the plastic foil roof either opens or closes completely or partially. The roof portions hang vertically downwardly into the greenhouse letting in full daylight or sunlight when desired. When the two suspension line meet or are adjacent to each other in the center of the support structure, the plastic foil surface are nearly parallel to each other and are close together resulting in an opening of that portion of the roof.
If desired this hanging fold of plastic with its weight when the roof portion is open, may be rolled manually or otherwise upwards to effect an even more open roof.
It is an object of this invention to provide a greenhouse structure that includes a plastic foil or film roof adapted to hang vertically down in adjacent folds in a taut position both in the open and closed positions and which is safe for use in windy, rainy or snowy conditions.
Additional details of the construction and advantage of the invention are provided in the following detailed description of a preferred embodiment of the invention which is shown schematically in the drawings wherein like reference characters in the several views depict the same elements.